The core function of the grounding ring in an electromagnetic flowmeter is to establish a stable zero-potential reference point and ensure a reliable electrical connection between the measured liquid and the sensor signal.

Specifically, they serve several key functions:

Eliminating interference signals and stabilizing measurements
Electromagnetic flowmeters operate based on Faraday's law of electromagnetic induction; the induced voltage generated at the two detection electrodes is extremely weak—often just a few millivolts. Stray currents in the fluid (often caused by cathodic protection, electrolysis equipment, or nearby high-power machinery) can superimpose onto the measurement signal, causing significant errors. Grounding rings "lock" the potential of the fluid to that of the instrument's ground, shunting this interference directly to the earth.

Preventing electrode polarization and protecting electrodes
When measuring media prone to electrochemical reactions (such as acids, alkalis, or brine), a lack of proper grounding can lead to DC polarization potential between the electrode and the fluid, resulting in zero-point drift. Grounding rings provide a path for charge dissipation, preventing charge accumulation that could damage the electrodes or compromise measurement accuracy.

Meeting grounding requirements for various pipe materials

Metal pipes (without insulating liners): Being conductive, they theoretically do not require a separate grounding ring. However, installing a grounding ring (or grounding strap) is still recommended to ensure the integrity of the grounding circuit.

Plastic pipes (e.g., PVC, PP, or PTFE-lined): The pipe itself is insulating, isolating the fluid from the earth. A grounding ring is essential to make contact with the fluid and provide a connection point for the grounding wire.

Metal pipes with insulating liners: Liners (such as rubber or PTFE) isolate the fluid from the metal pipe wall; therefore, a grounding ring must be used.

Facilitating empty-pipe detection (specific models)
Some electromagnetic flowmeters equipped with empty-pipe detection capabilities utilize changes in capacitance or resistance between the grounding ring and another electrode to determine whether the pipe is full or empty.

Differences between two common types:

Standard grounding ring: Makes direct contact with the fluid and provides a zero-potential reference; suitable for most applications.

Grounding ring with integrated electrode: Features an additional electrode built into the ring; used to enhance measurement accuracy or enable specialized functions like empty-pipe detection or multi-electrode measurement.

A simple summary:
Electromagnetic flowmeters measure minute voltage signals. Without a stable ground reference, the signal is like trying to weigh something on a rocking boat—it will never be accurate. The grounding ring acts as the crucial component that stabilizes the boat (the fluid) and the scale (the instrument) on the same level plane. Installation Instructions:

Typically installed between the flanges at both ends of the sensor and the pipeline flanges (using the supplied gaskets).

A dedicated copper-core wire (cross-section ≥ 2.5 mm²) must be used to securely connect the grounding ring to the instrument's dedicated grounding terminal and then to an earth ground (recommended grounding resistance < 10 Ω).

Do not connect the grounding ring directly to the equipment's protective earth (PE wire) or wire it in series with it; doing so could introduce electrical grid interference.